lokahi: N-chain service composition and config

Grow rust/lokahi from the #22509 skeleton: per-chain actor groups via the shared composition entry point, the multi-chain L1 watcher, layered config (global + per-chain overlay reusing kona-node's config types), per-chain data dirs and RPC namespacing, chain-labeled metrics, process-wide fail-fast (a fatal actor error exits the node; EL outages are transient retries). Cross-safe = trivial promotion at this stage (N independent kona-nodes in one process). Wire the CI touchpoints for new crates/binaries (workspace membership, persist globs, check-no-std list if no_std).

Depends on: #22530, #22531, #22529.

🤖 *Co-created with Claude (Fable 5)*

Start in rust/lokahi and trace the shared composition entry point, then review the prerequisites in #22530, #22531, and #22529. Verify the design for per-chain actors, layered configuration, data and RPC namespacing, metrics, failure handling, and the listed CI touchpoints before implementing; done means the independent kona-nodes compose and the required CI checks pass.

Written by the indexing model from the issue text.